Broad-band absorption and photo-thermal conversion properties of zirconium carbide aqueous nanofluids

Broad-band absorbers are very important for solar thermal utilization. However, seeking ideal solar absorbers whose absorption spectra match well with the solar spectrum is still a great challenge. In this work, zirconium carbide (ZrC) nanofluids with broad-band absorption characteristic were prepared by milling and dispersing ZrC nanoparticles in water. The ZrC nanoparticles show strong optical absorption in the range from 300 to 2000 nm. At a penetration distance of 1 cm, the ZrC nanofluids of 0.02 wt% can absorb almost 100% of the solar irradiation in the full spectrum and the solar weighted absorption coefficient (A(m)) is 0.99. The results indicate that the ZrC nanofluids of 0.02 wt% are very close to the ideal solar irradiation absorbers. The photo-thermal conversion efficiency of the ZrC nanofluids was evaluated by a direct method focusing on the nanofluids themselves instead of indirectly represented by the efficiency of the solar thermal collector as presented in the previous reports. By recording and analyzing the temperature rise of the nanofluids under the illumination of a solar simulator, the photo-thermal conversion efficiency for the ZrC nanofluids of 0.02 wt% was determined to be 92%. The high efficiency is attributed to the broad-band absorption of the ZrC nanoparticles. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.